In course of the fabrication of electronic devices, a substrate and layers disposed over the substrate are patterned using lithography techniques, wherein both in the substrate and in individual ones of the layers line-shaped and/or dot-shaped features may be formed. According to existing approaches in semiconductor production environments, spectrometrology methods (e.g., scatterometry or ellipsometry) process the spectral response of sections of a semiconductor wafer. Model-based fitting algorithms then, by varying the model parameters, fit the actual spectral responses with reference spectral responses calculated from a model of the respective sections in order to determine the parameters of the respective wafer sections, like the dimensions of the line-shaped or dot-shaped features in/on the substrate or in/on one of the layers.
With shrinking feature size, enhanced patterning techniques like pitch fragmentation and double exposure methods become of increasing interest, wherein, for example, the odd lines of a regular line arrangement including a plurality of parallel lines emerge from another process and may have another mean line width than the even lines of the same line arrangement. If further the material of the even lines is the same as that of the odd lines, then, though the spectral response does reflect the two mean line widths, the evaluation of the spectral response leaves open which of the lines are the narrow ones and which are the wide ones. Only after additional measurements like scanning electron microscopy, the measured line widths may be assigned to the correct type of lines (i.e., the even or the odd ones).
In light of the deficiencies of the above discussed approaches to determine feature dimensions like line widths, a need exists for improved methods and for suitable measurement marks for the determination of feature dimensions and/or for improved process control.